IS 12257( LP W-Fa"ts `qT;T% Part 2):1992 ( Reaffirmed 2006 ) Indian Standard PNEUMATICMEASUREMENT PART 2 DESIGN FEATURES OF INSTRUMENTS WORKING IN HIGH PRESSURE RANGE UDC 531*713*08~32 @ BIS 1992 BUREAU MANAK OF BHAVAN, INDIAN 9 BAHADUR NEW DELHI STANDARDS SHAH 110002 Price Group 3 ZAFAR MARG February 1992 Engineering vetrology\>Sec$onal Committee, LM 05 FOREWORD This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the Engineering Metrology Sectional Committee had been approved by the Light Mechanical Engineering Division Council. Air gauging has been gaining wider acceptability in industry because ~of its accuracy, consistency and reliability. These can be used for on line measurement of parts as they are being machined and take corrective actions. It mainly consists of gauging element and an indicating instrument. Gauging elements have been classified as `non-contact' type land `contact' type. Various instruments covered -in the standard operate at input pressure ) 50 kPa. This standard has been published in various parts. Other parts-of this standard are: Part I General information on principles and method Part 3 Parameters of instruments working on high pressure Part 4 General information and examples of application In the preparation of this standard assistance has been derived from the following: DIN 2271 Part 2, Deutsches Institut fiir Normung, DIN Glossary of terms and definition used in air gauging - NPL UK Principles of pneumatic gauging - NPL UK IS 12257 ( Pat 2 )-cl992 Indian Standard PNEUMATXCMBASURBMBNT PART 2 DESIGN FEATURES OF INSTRUMENTS WORKING IN HIGH PRESSURE RANGE 1 SCOPE This standard deals with pneumatically opera&d instruments for dimensional measurements consisting of a gauging element and an indicating instrument which operates on an input pressure of pl > 50 kPa ( 0.5 bar ) that is high pressure according to IS 12257 ( Part 1 ) : 1987. 2 REFERENCE IS 12257 ( Part 1 ) : 1987 `Pneumatic measurement : Part 1 General information on principles and methods' is necessary adjuncts to this standard. 3 GAUGING ELEMENT Gauging elements are used to determine the variable dimension on the component being tested. They are basically divided into gauging elements of the non-contact type and those -which operate with mechanical contact. They are suitable for measurement of internal and external dimensions as well as form and positional variations. 3.1 Gauging Elements Non-contact Type In the case of gauging elements of non-contact, the air flows from the measuring or the sensing jet directly on to the surface of the object being tested which serves as the deflector plate [ see IS 12257 ( Part 1 ) : 1987 1. 3.1.1 Air Plug Gauge Open Jet genera~by has two measuring jets on its circumference (-in special cases there may be several measuring jets ). Jet 3.1.2 Air Ring Gauge and Snap Gauge - Open The open jet air ring nal measurements ( As in the case of air have two measuring jets. gauges are used for exterthat is, shafts, see Fig. 2). plug gauge, these generally jets or several measuring Jet 3.1.3 Air Probe --Open The open jet air probe with a standard clamping diameter of 8 h6 is used on measuring tables in fixtures, etc, that is, on comparator stand asa dial gauge ( see Fig. 3 ). 3.2 Gauging Element Contact Type In the case of mechanical contact gauging element, mechanical contact is made with the object under test. The displacement of the contact due to dimensional change brings about a change of gap between the measuring jet and a deflector plate. The measuring jet and the plate are connected to form an assembly. 3.2.1 Mechanical Contact Air PIug~Gauge Each of the measuring jet of a mechanica contact air plug gauge ( see Fig. 4 ) has a ball at its end which is pressed outward against the surface of the object being tested by the air flowing out of a spring. Mechanical air plug gauges are used for internal measurements. The open jet air plug gauge is used for internal measurement ( that is, holes, see Fig. 1 ). It MEASURING JET r FOR MEASURING JET FOR THROUGH HOLES BLIND HOLES FIG. 1 AIR PLUG GAUGE - OPEN JET 1 1 JET RING GAUGE JET GAP GAME FIG. 2 AIR RING GAUGE AND SNAP GAUGE - OPBN JET Lever 3.2.2 Mechanical Contact Air Plug Gauge or Leaf Spring Contact Air Plug Gauge ,_@8h6 I- Each of the measuring jet is fitted with a movable probe ( leaf spring or a lever ) which is pressed against the surface of the object being tested ( see Fig. 5 ). MEASURING IURING JET JET FIG. 3 AIR PROBE - OPEN JET FIG. 5 MECHANICALCONTACTAIR PLUG GAUGE - LEVER OR LEAP SPRING CONTACT AIR PLUG GAUGE MEASURING JET 3.2.3 Mechanical Contact Air Ring Gauges These are designed similarly to the mechanical contact air plug gauges according to 3.2.1 and 3.2.2. 3.2.4 Me.chanical Contact Air Probe FIG. 4 MECHANICAL CONTACTAIR PLUG GAUGE 2 Mechanical contact air probe measure the dimension by mechanical contact with the surface of the object being tested. The displacement, due to size variation of the pin brings about a gap change in the probe between the measuring jet and the deflector plate ( see Fig. 6 ). URING JET is a clear glass tube with a calibrated internal diameter which widens out towards the top in accordance with a specific function that is the magnification of the instrument. The floating body floats freely within the measuring tube and stabilises at a certain height according to the flow. This flow changes due to the change of clearance between the gauging jet and the deflector plate or the surface of the object being tested. 4.1.2 In a column type indicating instrument which uses the pressure measuring method ( see Fig. 8 ), the straight vertical scale of a fluid manometer serves was the indicator: FIG. 6 MBCHANICALCONTACTAIR PROBE 4.2 Indicating Instrument with Circular Dial ( See Fig. 9, 10 and 11 ). instrument [ as Indicator or the indicating described inlS 12257 ( Part 1 ) : 1987 ] is in this case a pressure gauge, dial gauge or other similarly operating instrument. 5 REGULATING ELEMENTS AND ADJUSTING 4 INDICATING INSTRUMENTS Indicating instruments are basically magnifiers used to magnify the dimensional change detected by the gauging element. That part of the which includes the indicator [ see circuit IS 12257 ( Part 1 ) : 19871 and the pressure regulator generally forms an integral part of the indicating instrument. 4.1 Column Type Indicating Instruments with Straight Vertical Scale 4.1.1 In a column type indicating instrument which uses the volumetric flow method ( see Fig. 7 ), the measured value is indicated on a straight vertical scale by means of a floating body in a measuring tube. This measuring tube 5.1 Pressure Regulator The pressure regulator reduces and regulates the supply pressure in the line to the measuring to the system pressure of the instrument measuring instrument with a required degree of accuracy. HT VERTICAL `NT FIG. 7 COLUMN TYPE INDICATING INSTRUMENT WITH STRAIGHT VBRTICAL SCALB 3 FLUID Mh+OME.TER COMPENSATING VESSEL ~r\HL"lll VEPTICAL SCALE SHUT-OFF VALVE Ill%-_-!4 1 - /COMPRESSED -AIR-FILTER PILOT JET V /GAUGING ELEMENT FIG. 8 COLUMN TYPE JNDICATINGINSTRUMENT USING PRESSURE MBASURING METHOD PRESSURE REGULATOR PRESSURE ING GAUGE ELEMENT INDICATING G FIG. 9 INDICATING INSTRUMENT USING THE-PRESSURE MEASURING METHODWITH A SIMPLBPRESSURE GAUGE SHUT-OFF VALVE GING ELEMENT FIG. 10 INDICATING INSTRUMENT USING THE PRBSSURE MEASURING METHODWITH A DIFFBRBNT~AL PRESSURE GAUGB 4 IS 12257 ( Part 2 ) : 1992 T-OFF VALVE FIG. 11 INDICATING INSTRUMENT USING THEPRESSURE MEASURING MBTHOD WITH A DIAL GAUGE 5.2 Zero Adjuster The -zero adjuster alters the position of the zero either pneumatically with the linearity range or by adjusting the mutual position of the indicator and scale. 5.3 Compensation In the case of indicating instruments with compensation; the conversion can be altered in small ranges to suit the gauging element or the indicating instrument. 5 Standard Mark The use of the Standard Mark is governed by the provisions of the Bureau of Indian Standards Acr, 2986 and the Rules and Regulations made thereunder. The Standard Mark on products covered by an Indian Standard conveys the assurance that they have been produced to comply with the requirements of that standard under a well defined system of inspection, tosting and quality control which is devised and supervised by BIS and operated by the producer. Standard marked products are also continuously checked by BIS for conformity to that standard as a further safeguard. Details of conditions under which a licence for the use oft he Standard Mark may be granted to manufacturers or producers may be obtained from the Bureau of Indian Standards. lhweau of kndiaq,Standards :.a~ i: s, BIS is a statutory institution established_ under the Bureau of Indian Standards Act, 1986 to promote harmonious development of the activities of standardization, marking and quality certification of goods and attending to connected matters in the country. 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